scsi: lpfc: lpfc_hbadisc: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Notice that, in this particular case, I replaced "Drop thru" with a
"fall through" annotation, which is what GCC is expecting to find.

Addresses-Coverity-ID: 114976 ("Missing break in switch")
Addresses-Coverity-ID: 114977 ("Missing break in switch")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>